Abstract: AimTo study the antitumor effect of baicalein on human leukemia K562 cell and its mechanism. MethodsThe IC₅₀ value and cytotoxity of K562 cell were detected by MTT method. The apoptotic cell was analyzed by FCM using Annexin V FITC - PI staining method. Sub-G₁ peak was also measured by FCM. Protein expressions of Bcl-2，Fas， Caspase 3 were evaluated with FCM. ResultsBaicalein was shown to significantly inhibit the proliferation of K562 cell in a dose-dependent manner and selectively induce apoptosis of human leukemia K562 cells. Flow cytometric analysis showed that baicalein arrested K562 cells in the S phase. In addition, protein expression of Fas，Caspase 3 of K562 cells increased after exposure to baicalein, but Bcl-2 was unchanged。ConclusionBaicalein can selectively induce apoptosis of human leukemia K562 cell dose and time dependently through up-regulation of caspase-3 and fas gene expression level.